Could a Massive Volcanic Eruption Have Led to Napoleon's Loss at Waterloo?

Losing parties often have excuses for why they came up short. If you’re playing softball, maybe the sun got in your eyes. If you drop a Monopoly game, maybe someone cheated and squatted on Park Place. And if you’re Napoleon Bonaparte, maybe an Indonesian volcano helps explain why you lost the Battle of Waterloo.

Obviously, Napoleon isn’t around to lay blame for his defeat in Belgium in 1815, a conflict that ended his long reign as France’s emperor and premier military strategist. But recent research into how volcanic eruptions can influence weather patterns might be able to offer insight into why Napoleon made the fateful choice of delaying engagement against the Duke of Wellington’s forces 12 miles south of Brussels.

A paper published in the journal Geology [PDF] and authored by Imperial College earth scientist Matthew J. Genge offers new information about how high volcanic ash can rise following an eruption. Previously, it was believed ash could reach as high as the stratosphere, or 31 miles above Earth’s surface. Genge’s research, based on computer modeling, suggests that an electrostatically charged volcanic plume could force the ash even further, sending it 50 to 600 miles up and into the ionosphere, where the particles can cause cloud formation and precipitation.

Two months before Napoleon arrived on the scene at Waterloo, Mount Tambora in Indonesia exploded, likely sending ash into the ionosphere. More than 8000 miles away from Belgium, the ash scattered for months, slowly migrating to Europe. Some climate historians have inferred that the resulting precipitation in Belgium created a waterlogged battleground for Napoleon and the opposing Prussian and British armies. It was this muddy, uneven terrain that likely prompted Napoleon to hold off advancing until the middle of the day, allowing his rivals to gather their forces and eventually forcing his retreat.

While Mount Tambora’s eruption was devastating—it killed 100,000 people on the island of Sumbawa and forced a global temperature drop of more than 5°F in 1816—the theory that it led directly to Napoleon’s defeat is hard to substantiate. While waiting until later in the day to attack and having unsure footing didn’t help, Napoleon's opposition was fighting in the same conditions and may have outmaneuvered him regardless. In one key sequence, he failed to follow up on an effective artillery attack, allowing Wellington to compose his forces and make a successful bid to end the scuffle.

Genge draws heavily on the behavior of volcanic ash from two subsequent massive eruptions—Indonesia's Krakatau in 1883 and the Philippines's Mount Pinatubo in 1991—to illustrate his “short-circuited” theory of ionosphere disruption, and not from Tambora specifically. While rain may have indeed altered Napoleon’s plans, it may not necessarily have been the result of Tambora. Genge's work will, however, likely inspire further investigation into how inclement weather may have changed the course of history.